Just like humans, it is common for dogs to suffer from heart conditions. In this post, our Dallas vets talk about mitral valve disease in dogs, how to spot it and what treatment is available.

What is the Mitral Valve?

The heart has four chambers. The upper chambers are called atria (the right atrium and left atrium) and the lower chambers are called ventricles (right ventricle and left ventricle). The heart is also divided into right and left sides.

Each chamber of the heart has a one-way valve to keep blood from flowing backward. The valve between the left atrium and left ventricle is called the mitral valve.

What Causes Mitral Valve Disease in Dogs?

Because of the high pressure created when the left ventricle contracts and pumps blood out to the body, the mitral valve may begin to ’wear out’ and leak over time. This is known as mitral valve insufficiency or mitral regurgitation and is often associated with a heart murmur.

Other causes of mitral valve insufficiency include ruptured chordae tendinae, a condition in which the fibrous cords that hold the valve position break, and heart valve infections known as endocarditis. Endocarditis may result from blood-borne infections or, more commonly, may be secondary to chronic periodontal disease.

Symptoms of Mitral Valve Disease in Dogs

Many dogs with mitral valve disease are asymptomatic with the only clinical sign being a heart murmur that would be heard by your veterinarian. Mitral valve insufficiency and disease will cause turbulent blood flow through the heart that results in a heart murmur. As the disease progress, clinical symptoms dog owners may notice include:

Coughing
Exercise intolerance
Increased respiratory rate and panting
Sudden collapse
Weight loss

What Causes Congestive Heart Failure In Dogs

The most common cause of congestive heart failure in dogs is congenital heart defects, meaning that it's an unpreventable genetic condition. Many small breeds have a genetic propensity toward CHF including toy poodles, Pomeranians, dachshunds, and cavalier King Charles spaniels. Small dogs in general tend to be more prone to developing CHF becuase their heart valves are more prone to degenerate than in larger breeds. However, some large breeds, particularly giant breeds such as St. Bernards, Newfoundlands, and Great Danes are prone to developing CHF due to dilated heart muscles. It's important to understand that congenital CHF typically appears later in a dog's life and that these dogs can live many years seemingly healthy and happy before symptoms begin to show.

CHF can also develop in a heart that's been weakened by other heart conditions, so it's important to do what you can to prevent heart disease from occurring in your pet, including preventing obesity and providing heartworm prevention.

How is Mitral Valve Disease in Dogs Diagnosed?

Your veterinarian will first perform a physical examination and listen to your dog's heart with a stethoscope. A heart murmur in a specific location is indicative of mitral valve disease. If your veterinarian suspects mitral valve disease, they may order other diagnostic tests such as:

Radiographs (x-rays) - useful for assessing cardiac size and chamber enlargement. X-rays are also valuable in detecting fluid accumulation in the lungs called pulmonary edema
Echocardiogram (ultrasound of the heart) - this is a beneficial test as it can directly assess the mitral valve. It can also detect turbulent blood flow through the mitral valve and measure the thickness of the heart.
Electrocardiogram (ECG or EKG) - this test may be recommended if your veterinarian detects an arrhythmia when listening to your dog's heart.
Blood work (biochemical profile and CBC) - baseline blood work is helpful as it allows your veterinarian to obtain an overall health status for your dog. In addition, 25% of all the blood that leaves the heart (cardiac output) is provided to the kidneys. If there are compromises to heart function, elevated kidney levels may be noticed.

Treatment Options For Mitral Valve Disease in Dogs

A leaky heart valve can be replaced surgically in people. However, this is usually not feasible in dogs. However, there are several drugs and treatments that will improve heart function, including:

Angiotensin converting enzyme (ACE) inhibitors

ACE-inhibitors work by lowering blood pressure and reducing the after-load or resistance to blood flowing out of the heart. They are one of the most powerful and commonly used classes of drugs for heart disease in both humans and pets. ACE-inhibitors are the only drugs proven to extend life expectancy in both people and dogs. Enalapril and benazepril are commonly used ACE-inhibitors in dogs.

Diuretics

These are drugs that stimulate the kidneys to remove excess fluid from the body. Furosemide and spironolactone are the most commonly used diuretics in veterinary patients.

Nitroglycerin

This drug dilates the veins throughout the body, especially the ones leading to the heart muscle. This permits better heart contractions and allows blood to move more freely to the other body tissues. However, it is only effective for one to two days before the body builds tolerance (resistance) to it. Therefore, it is usually only used during a crisis. It is often applied topically in an ointment form.

Cardiac glycosides

These drugs improve heart function in several ways, including regulating the release of hormones, slowing the heart rate, and strengthening each contraction of the heart. Digoxin is the most common glycoside drug used in veterinary medicine. Digoxin can have several potentially harmful side effects and must be carefully monitored and regulated.

Vasodilators

These drugs dilate the arteries and veins of the body to permit better blood flow. They may be used long-term because they continue to be effective, as opposed to the short-term effects of nitroglycerin. They are effective long-term treatments for patients with MVI. ACE-inhibitors are the vasodilators used most widely in the therapy of CHF due to MVI.

Beta-blockers

Drugs such as propranolol, atenolol, sotalol, and carvedilol are used in some cases to slow the heart rate and lower blood pressure. Carvedilol has shown very favorable effects in treating human heart failure and is gaining acceptance in veterinary medicine as new research is conducted.

Inotropes

These are drugs that are used to help improve heart muscle strength and they also lower the pressure in the arteries and veins. Pimobendan is more often used in advanced stages of heart failure but may be used in some mild to moderate stages of mitral valve disease as it could slow down the progression. More research is being done in this area as this is still of some debate.

Low salt diet

Dietary salt restriction may help prevent retention of excessive fluid in the body. Several low-salt or low- sodium veterinary prescription diets are available.

Not all of these treatments are used in an individual case of heart failure. The results of the various tests will determine which ones are appropriate for your pet's condition. Your veterinarian will choose the appropriate medication(s) to treat your dog with.

What is the Prognosis for Dogs with Mitral Valve Disease?

There are many factors that must be considered before that question can be answered. The results of the diagnostic tests are important and your pet's response to treatment is another indicator. If a favorable response does not occur within a few days, especially in more advanced cases, the prognosis is not good. However, most dogs that stabilize quickly will live a good quality of life that with treatment is extended for many months or a few years.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.

Is your dog showing symptoms of mitral valve disease? Contact New Hope Animal Hospital today to get a proper diagnosis so our veterinary team can get ahead of this serious condition.

Mitral Valve Disease Dogs